Referring now to FIGS. 1A and 1B, different temperature control systems used in vehicles to control cabin temperature are shown. In FIG. 1A, a manual temperature control (MTC) system 10 is shown. The MTC system 10 comprises user controls 12, an air-conditioning (AC) control module 14, a compressor 16, a blower 17, and an evaporator 18.
An occupant uses user controls 12 to manually set and adjust the cabin temperature. For example, the occupant can set a desired cabin temperature, adjust a speed of the blower 17, and/or turn the AC on or off. The AC control module 14 controls the compressor 16 based on the settings input by the occupant and by sensing the temperature of the evaporator 18. When the user turns the blower 17 on, the blower 17 blows fresh air from outside the vehicle into the cabin or recirculates the air in the cabin depending on an airflow mode selected by the user.
In FIG. 1B, an automatic temperature control (ATC) system 20 is shown. The ATC system 20 comprises the user controls 12, an AC control module 22, the compressor 16, the blower 17 and the evaporator 18.
The occupant initially sets the desired cabin temperature. Thereafter, the ATC system 20 automatically maintains the desired cabin temperature based on inputs received from interior and exterior of the cabin and by sensing the temperature of the evaporator 18. Additionally, the AC control module 22 controls the blower 17 and selects the airflow mode. When the AC control module 22 turns the blower 17 on, the blower 17 blows fresh air from outside the vehicle into the cabin or recirculates the cabin air depending on the airflow mode selected.
Typically, the ATC system 20 maintains the desired cabin temperature by turning the compressor 16 on and by maintaining an evaporator temperature at a low value (e.g., 35 F to 38 F). When the evaporator temperature is maintained at the low value, however, the compressor 16 is turned on at all times. Consequently, the ATC system 20 increases energy consumption and decreases fuel efficiency of the vehicle.